Thank you gentlemen for the advice. Is there a "definitive" Luger book that you can recommend? Price, while always a variable, is not as important as the correct book.
For now, I am going to use this list found on this forum.
Some pretty good starter books that cover the "General" category are:
1) Kenyon's "Lugers at Random"
2) Walter's "The Luger Book"
3) Costanzo's "World of Lugers"
Not necessarily in that order!!
I also like Jan Still's books for period Lugers:
1) "Imperial Lugers"
2) "Weimar Lugers"
3) "Third Reich Lugers"
Then, you could get some ancillary books, like:
1) Bender's "Luger Holsters and Accessories"
2) Goetz's "German Small Arms Markings"
Bittrich